<template>
  <div class="spec-preview">
    <img :src="defaultImg.imgUrl" />
    <div class="event" @mousemove="move"></div>
    <div class="big">
      <img :src="defaultImg.imgUrl" ref="bigImg" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: 'Zoom',
  data() {
    return {
      // 设置初始值 默认挂载后显示第一张图片内容
      detaultIndex: 0,
    }
  },
  props: ['skuImageList'],
  computed: {
    defaultImg() {
      return this.skuImageList[this.detaultIndex] || {}
    },
  },
  mounted() {
    this.$bus.$on('changeIndex', (index) => {
      this.detaultIndex = index
    })
  },
  methods: {
    move(e) {
      let mask = this.$refs.mask
      let bigImg = this.$refs.bigImg
      // 获取鼠标位置
      let mouseX = e.offsetX
      let mouseY = e.offsetY

      // 遮罩对应移动位置
      let maskX = mouseX - mask.offsetWidth / 2
      let maskY = mouseY - mask.offsetHeight / 2

      // 判断是否超界
      if (maskX < 0) {
        maskX = 0
      } else if (maskX > e.target.offsetWidth / 2) {
        maskX = e.target.offsetWidth / 2
      }
      if (maskY < 0) {
        maskY = 0
      } else if (maskY > e.target.offsetHeight / 2) {
        maskY = e.target.offsetHeight / 2
      }
      mask.style.left = maskX + 'px'
      mask.style.top = maskY + 'px'

      bigImg.style.left = -2 * maskX + 'px'
      bigImg.style.top = -2 * maskY + 'px'
    },
  },
}
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
